Thráin and his people settled in the Blue Mountains in III 2802, but we know little of Dís' history after this date. She was said to have been one of very few female Dwarves among this people, and it is clear that at some point in the following decades she chose a husband. Nearly sixty years after her arrival in the Mountains, Dís had a son, Fíli, and five years later another, named Kíli. With her elder brother Thorin being childless, and Frerin having been slain in battle, Dís' sons were therefore the heirs of the royal line of Durin's Folk.4

Of Dís' later life we know almost nothing. She was likely still alive in III 2941 (when she would have been 181 years old - not extraordinarily old for a Dwarf), when she would have seen her brother Thorin set out on the Quest of Erebor, taking her sons Fíli and Kíli among his party. Thorin's company succeeded in reclaiming Erebor, but Thorin himself, and both of Dís' sons, were slain in the attempt. After this, many Dwarves gathered at the newly-refounded Kingdom under the Mountain, but we have no way to know whether Dís herself made the journey back to her childhood home. If she lived a typical Dwarf lifespan, Dís would have lived until about the year III 3010, thus not surviving to see the War of the Ring and the end of the Third Age.

Dís is notable as being the only Dwarf-woman recorded in the histories of Middle-earth. The Dwarves were in general highly secretive about their womenfolk, and very little is known about their place in Dwarf society. They were said to make up only about a third of the population, and be physically almost indistinguishable from male Dwarves (at least to the eyes of a non-Dwarf). Among the Longbeards, and perhaps therefore among all Dwarves, women do not appear to have been able to inherit titles, but they seem to otherwise played a relatively independent role in Dwarf society. We're told, for example, that many chose not to take husbands (a fact that accounts for the generally low rate of increase in Dwarf populations).

Notes

1

Our last definite dated, albeit indirect, reference to Dís is III 2864, when her youngest son Kíli was born. At this date Dís would have been 104 years old, a less remarkable age for a long-lived Dwarf than it may seem. Assuming a typical Dwarf lifespan, Dís probably survived until about the year III 3010.

2

As is commonly the case for Tolkien's Dwarves, the name Dís comes from Old Norse, though its translation is far from straightforward. In its original language, it is most commonly seen in the plural form Dísir, which seems to have meant something like 'female spirits' or 'goddesses', with the Valkyries being the most familiar of these supernatural Dísir. The singular form Dís can be interpreted as simply 'lady' (and this is probably how Tolkien intended it to be taken, since Dís the Dwarf was by no means supernatural), though its mythological associations mean that it can also be translated as 'goddess'.

3

It's not entirely clear how Dís escaped the Sack of Erebor. We know that her brother Thorin survived because he was outside the Mountain when the Dragon descended, and we know that Dís' father and grandfather (Thráin and Thrór) were able to escape through the secret door in the mountainside. Dís isn't directly mentioned as being with either of these parties, so her means of escape remains unclear; all we can say for sure is that she definitely did survive the disaster.

4

Thorin had no children, so his direct heir would have been his younger brother Frerin. After Frerin was lost, we might wonder why Dís herself would not have been considered the heir. It should be said that it's nowhere explicitly said that she was not, though this is very heavily implied. There is in fact no record of a queen anywhere in the histories of the Dwarves, nor indeed any mention of a Dwarf-woman at all, with the sole exception of Dís. We can probably safely infer from this that the Dwarves, or at least the Longbeard clan to which Dís belonged, used a strictly patrilineal system of royal descent.